More than 2,000km of the southern coast of India was swamped by waves, including the state of Tamil Nadu, whose capital, Madras was particularly badly hit.
BBC News readers e-mailed us with their reports of the disaster
My friend Dilip's son Vikram had come home for Christmas from the US where he was doing management studies. Dilip arranged for a fishing expedition as a special treat on 26 December. When Dilip woke Vikram at 5am, Vikram cried off as he had been partying till 3am. Dilip and his driver drove out 20 miles south of Madras to Fisherman's Cove, where there's a creek from the sea. Dilip went waist deep into an inlet to cast his rod. His driver, who couldn't swim, stayed on the bank, when suddenly Dilip shouted to him to run. He saw his driver being carried off by a huge surge before he himself was caught and turned over and over and carried away.
A strong swimmer, Dilip discerned the left of him was where the creek broadened into a mile-wide lagoon and fought his way that way. Semi-conscious, he was driven past a group of rocks and thorn bushes, and while being battered kept clutching at the bushes and eventually managed to stop with his head in a thorn bush. From there a passing cyclist took him out and handed him to a motorcyclist who delivered him to a beach hotel at the top of the cove, whose beach cottages (but not the main building) had been destoyed by the wave. The driver was tossed around and grabbed a palm tree trunk which deposited him a mile down the creek. Bleeding and distraught, a car picked him up and took him to Madras where he crawled in on all fours to Dilip's mother's house and wailed that he had seen Dilip drowned.
Senphilip, Madras, India
In Pondicherry main beach you can't sea any sand at all, but that morning by dad and uncle woke me up saying that suddenly water had disappeared from the beach. I thought they had gone mad. Fortunately in the main beach of Pondicherry the waves were not as high as in Chennai or Sri Lanka, otherwise thousands who had gathered there could have died. The police stopped the people going to the beach only an hour after the tsunami started hitting Chennai
Pradeep, Pondicherry in India
I live in an apartment on the second floor situated on a narrow street connecting the beach (a little away from Marina) with my family hardly a kilometre away. I was lying down when I heard sounds of people screaming and running. Ran to the balcony only to find people carrying old people in their arms, mothers firmly clutching their children. I couldn't understand why these people were running. In a matter of seconds, I saw water gushing from the pathway that lead to the beach. It was gushing like a river. This happened for at least 5 secs but they seemed like an hour. It was a frightening sight. There was knee deep water and the tsunami toppled the huts like a pack of cards. Mothers were wailing that they had lost their children in the pandemonium. I didn't realise the intensity of the incident till I saw it on the television. This incident made me come to one conclusion that man is powerless next to mother nature.
Shilpa Samuel, Madras, India
Suddenly at about 0905 we heard a sound that resembled a tipper lorry unloading rocks. The wave that came in was not very tall - maybe about one or 1.5 metres high but was a mass of water that was scary. Water rose to about two or three feet on our land and we managed to save one girl who was trapped inside a hut. After three hours of help and rescue when we realised that the waves were coming in a cyclic pattern, we packed into our cars and went inland. I am told that several children are still missing and that the police have cordoned off the East Coast Road. One shudders to think what the magnitude of the tragedy would had it been night and the villagers were sleeping.
Navaz Currimbhoy, India - Madras
There are lot of rumours floating round, warning of more tsunamis. Most of the apartment blocks are deserted with people moving inland. The relief effort is hampered due to the sheer size of the tragedy - there is more than 40 kilometres of coast line with over 12 fishing hamlets in Chennai alone.
Vijay, Chennai, India
We are on a drill ship about 100 miles off the coast of India, near Kakinada. We are in 3,000ft water depth, but even so experienced a large swell of around 2 metres pass through about 1030 local time. We are also experiencing swells from the after shocks. Our supply base, in Kakinada, has been clobbered, luckily with no casualties, and the port area has been evacuated.
Bob Forrest, Discoverer Seven Seas, Bay of Bengal
We were swimming in the sea, when the first wave hit us, and so we sprinted out of the water. We went back in a few minutes and started swimming again. All of a sudden, we were yelled at to get out quickly as the waves were getting too strong. Our clothes were lost in the sea.
Maddy Scragg and Serena Starr, Kerala, India
There were small tremors which woke residents of Madras up. The tremors were mild and must have lasted a few minutes at most. It appears that after 0830 the waves hit the seashore and caught early morning joggers on the beach by surprise. Incoming seawater surged into the shores and some cars and vehicles parked on the road adjoining the beach were washed aside and toppled. The worst hit were the fishing folk who live in huts very close to the sea and it does appear that a large number of them are missing or are now homeless.
Vasan S S, Madras, India